Air filter



Jan. 23,' 1934. V, DAHhMAN 1,944,407

, AIR'- FILTER Filed Dec. si. 195o ZJ O AEZ /o Z /ZO Zo/o Z0 505/425 Z3 /0 YPatented Jan. l23, 1934 UN1TED STATES PATENT ol-Flc AIR FILTER Verner Dahlman, New Lenox, Ill., assigner to Independent Air Filter Company, Chicago, Ill., a corporation of Illinois Application December 31, 1930 serial No. 505,700

14 Claims. (Cl. 183-71) The present invention has to do with air filters and relates particularly to a filter in which a dry 'fabric sheet form is used.

The filtering of air is by no means a novelty.

For many years air has been passed through vfabric of Various characteristics for the purpose of purifying' such air. Some ofthe earliest forms of filters for air utilized fabrics` of fine or close texture but porous enough to admit of the passage specific uses, certain of the materials named have highly desirable qualities, iwhile for another purpose vother of the materials are superior. The

better practice of the present day is to select'the specific material which for the object in View possesses the greatest number of advantages and the fewest disadvantages.

In the present invention, any one of the materials hereinabove named may be employed, it being necessary only to form the filtering material into al sheet capable of being rolled or packaged for convenience in transportation and handling.

' The primary object of the present invention is to take full advantage of the remarkable air filtering qualities inherent in the fabrics named and to other materials suitable for air filtration'.

The present invention aims to concurrently over-'- come the objections which have heretofore prevented the more general use of air filters and of 40 the materials naturally adapted for air filtration. It is ele entary in the art of filtering air by this method th t the velocity of an air current through a fabric medium must be relatively low. In this respect, air filtering throughv fabric differs essentially from the so-called fimpingementmethod of air filtration, in which latter method the air is forcedto pass through a coarse maze of filaments, usually metallic in nature and usually coated with an `adhesive liquid such as oil.

In the` impingement method of air filtration, the cleaning of the air is obtained bycausing the dust particles in the air to impinge violently against an adhesive surface, the adhesive retaining the dust particles and allowing the air to move through freed of mechanicalfimpurity.

Obviously, the impingementmethod of vfiltration not only permits of a high air velocityy through the air filter, but for greatest efficiency -an oil filter of this type actuallydepends upon very high air velocity.

In the so-called dry air filters, high air velocity is impracticable. The texture of the filtering material'necessarily has relatively small pores. At high velocity, the resistance to air fiow could be objectionable, and the dust A.particles would be made to penetrate the fabric. The texture of the filtering medium and the pores thereof would fill rapidly with the dust particles driven forcibly thereinto, thereby clogging the filtering medium.

There is no exact standard determining the -velocity of air permissible through any fabric.

The permissible velocity of the air depends to a considerable extent upon the nature of the fabric itself. Another factor in determining the appropriate air velocity isthetype of dust to be removed from the air and the quantity of such dust contained in or carried by the air to be filtered.

For example, canton fiannel may be used as the arresting or filtering medium in atmosphere containing a heavy concentration of dust. Under. such conditions, air velocities as low as two lineal feet per minute are frequently employed. This velocity may be increased if the concentration of dust is in a lesser degree or if a filtering medium is selectedwhich possesses a more open character. l

In the cleaning of ordinary atmospheric air, where it is not necessary to stop themicroscopic particles of dust, a velocity of 20 to 30 feet per minute is not objectionable. In between these extreme velocities, namely, from two feet a minute to thirty feet a minute, the most efficient velocity must be determined by actual test made underworking conditions.

Several facts stand out in respect to dry air filters using media of the character herein described or similar media. One of these facts is that-a fabric medium will filter effectively regardless lof how low the velocity of air through the medium. A second fact is that the lower the velocity of the air to be ltered, the less will be the penetration of dust particles into the texture 'or body of the filtering fabric.

Another fact developed from practice is that when the air velocity is very low, the dust particles will remain in the nap of the fabric employed gradually build up a filter mat ofV themselves with the result that resistance to air flowwill be deand eventually these arrested dust particles willl veloped very slowly and the useful life of the filter medium thus greatlyv lengthened.

A fourth fact learned by observation of fabrics vin air iilters is' that the benents to be derived from low velocityare much greater than in direct proportion to such velocity. It may be said that the benefits to be obtained by low air velocity follow more nearly along the lines vof the law that "resistance to air flow varies as the squareof the.

velocity.

f A natural consequence or deduction which may v t or in a zig-zag form and nearly parallel to the air iiow, so that while the velocity of the air may be' fairly high where it enters the filter.

it is slowed down enormously as it passes through the fabric. The conventional devices for filtering air do not contemplate renewal of the fabric filter except at long intervals, as for example, one or more years.

Because of this need for large filtering area, aA

filter in which the filter medium can not be readily changed requires an excessive amount of space. Likewise, the conventional apparatus vof the present day, because of its Ibulkiness and its complicated structure, -is excessively high in cost.v A further `disadvantage of the conveni introduced has been limited and these conditions have retarded the rapid growth of air'filtration, notwithstanding the generally known advantages to be obtained by the employment of filtered air not only in the home but for many industrial uses.

The herein described apparatus adheres closely to the established principles above recited in the matter of, providing extensive area for the fllter medium. -It provides, however, such convenient means for renewing` the filter fabric thatthe servicing of the apparatus possesses no objectionable features. 1

While the instant apparatus provides ample filtering area in compact form, it renders unneccessary the provision of an excessive amount of filtering area because the renewal of the. iilter medium may be accomplished more readily in the instant apparatus'than in other'devices, all of which devices have a filtering medium incorporated into them more or less permanently.

- In the instant instrumentality, much higher airvelocities may-be employed than when the filter medium is permanent. The result is Athat the installation is thereby greatly reduced in size and in initial cost. The ease ofrenewal of the illter material makes it possible to keep the entire point which may be called'its break-down point.

There can be no approach to astate of ybreakdown in a system made up of the @tering unit herein which is easily4 recharged with `lter medium.

Another distinct advantage in the instant appa- Y such material, common cotton wadding may be employed. It is also adapted to use any form of sheet material as a iilter medium.

The instant device, by providing a unique method `of-i'olding a continuous strip of filter material makes it possible to use very flimsy filter materials, such as the two which have been mentioned, or any other filter mediumhaving only sufficient tensile strength to stand unwinding from a roll or `removal from another package.

In recapitulation, it is said that the advantages of the instant apparatus and its uniqueness depend upon the fact that'it provides an extensive area of filtering fabric while the device is in compact form, and the device at the same time provides a highly convenient means for renewal of `the filter material, the renewal being Aobtainable with such little effort that the systeinmay be kept in a constant state' of high efficiency.

'I'he additional objects of the invention include a unique compact arrangement of spacer elements whereby to facilitate the spreading of`a filtering tion of large cubical space by the filter; a new and unique unit for a dry filter medium in strip or roll form and having means for readily folding the said strip into parallel or substantially parallel layers, generally in parallelism with the flow of the air; an'improved filter unit having a plurality of spacer elements permanently but mov- `,ably attached thereto; a unique means for arranging and mounting spacer `elements in a filter unit; an improved form of filter spacing elementsyand a new and unique system of arrangement of spacer elements in a filter for facilitating the use of a strip or roll of lter medium. Y These objects, and such other objects, as may hereinafter appear, are obtained by the novel construction, unique arrangement, and improved combination of elements, all of which elements are illustrated in the accompanying'single sheet of drawing showing two forms of the invention.-

In said drawing:

Figure l is a front or back elevation of a iilter installation comprising a battery of filterqunits associated together;

Figure 2 is a horizontal section on the line 2-2 of Figure 1 looking in the direction of the arrows and illustrating one filter and parts of others;

Figure 3 is a vertical section taken on the line 3-3 of Figure 2 looking in the direction of the hinge arrangement of the`spacer elements employed and the course of air therethrough;

Figure 5 is an end elevation of a loading stand with a iilter such as is herein-described disposed thereon, in inverted position and ready to be discharged and loaded; and

Figure 6 is a fragmentary end detail showing the manner of mountingrods.41-42. v (i Like reference characters are used to designate similar parts in the drawing and in the description'hereinafter given.

In the present form of the invention, a plurai of lter units may be employed in a frame orho g. At least two ways of arranging these In such an arrangement each filter unit is closely fitted against the angle irons and a suitable seal between the frame and filter unitis provided.

A second method of mounting lter units is to provide each unit with a housing and then arrange a plurality of independent housings in a group, securing them one to another so as to form a rigid frame and of suitable dimensions.` Said casings, later described, may be joined together in any suitable manner either through their bodies or in theflange sections thereof. Asingle filter unit yis adapted to be removably secured in each casing or housing. Y

Each casing or housing 10 comprises a generally rectangular metallic or. other shell having flanges 11 at its front and flanges 12 at its back. In the corners of the flanges 12 at the rear, triangular members 13 `are suitable secured to act as stops for a filter unit, shortly to be described. Other types'of stops may be used, and the flow of air may be in either direction through the housing. The flanges 12 at the rear and flanges llv at the front may be formed in anysuitable manner, such flanges generally having outwardly extending shoulder sections 14.

Across any wall of the housing, generallythe top, there may be seals vgenerally ilexible members to obtain anV air tight closure between lter unit and casing. As seals are conventional, and their position a matter of choice, their inclusion in the drawing in this application has been considered unnecessary.

Each lter unit comprises a base 19 of sheet metal or other suitable material. `At each corner of said base 19 there is an angle iron 20, the short wing 21 of which angle irons form the front and back edges of the filter. The longer wing 22 ofv said angle irons. 20 projects inwardly from the outer edges of said base 19, of course, a changnel iron may be lsubstituted for an angle iron, and

other uprights could be selected.

At the top of the lter unit, there are two strips 23, each joining a front and a back angle iron 20, leaving the intermediate top of the\device open. Adjacent each top` corner of the lter frame, there is a transverse reinforcing1strip 24 which is in the form of a round tube, said tube member extends fromone narrow flange 2l to the oppo site narrow flange 21. Said member at its closed side projects outwardly of the filter frame in a horizontal plane to clear the spacers, later to be described, when said spacers are in open position.

A bottom cell or spacer 29 is secured upon the base 19 by any suitable means. Said spacer is arranged between the uprights 20. There is no air passage between the attached side -of the material of said spacer 29 and the base 19 itself. Said spacer member 29 comprises a closed back 30 and two closed sides 31 with an open front 32. The top 33 thereof has a foraminous section, the front edge 34 of the member being beaded. Sad front edgeniay be turned upwardly to provide an overlapping lip in relation to the next adjacent and movable spacer element, but this is not essential.

Above the xed spacer'29 is a movable spacer 35 comprising a closed back 36, closed sides 37, and foraminous tops and bottoms 38.

Beaded front edges 39 are at the open side 40 of said spacer. The bottom lip 39 depends along the top of the closed back 30 of the stationary spacer 29. The upper overlapping front edge 39 may be turned upwardly if desired and provide Aan overlapping portion with respect to the closed back of .the next movable spacer 35thereabove. Thev structure of said upper member 35 is the same as that of spacer 35 and it is similarly designated.

In the beads 39 at the open side of each spacer element 35. as illustrated. there are rods or wirel supports 41 and 42. Other fasteningmembers may beemployed, such, for example, as a flat st-eel stamping, so long as the spacers 35 are hinged and held captive. Said supports 41 and 42 may comprise bent Wire or rod-.like material adapted to project inwardly ofthe beads at the open side of the spacer elements 35. The mem- Ibers 4l and 42 converge in the direction of the base 19. Said members 41 and42 are brought together sothat the converged ends thereof may be jointly seated in asingle apertureat each side of the frame. The converging material of said members may be bent at an angle of ninety degrees and made to Aconjointly project through anv however, is' at'the opposite side of the device andin the opposed pair of tangle irons 20. Thus the movement of the spacers is in each instance the same, and the spacers are 'staggeredly arranged in the frame.

Spacers 35., like those described, extend upwardly one above another in alternate arrangement to the top of the lter. The top spacer 45 differs from the spacers 35 in that it has a foraminous inner facey 46and a closed outer face 47. Said -spacer 45, therefore,has,a closed back 47, a closed back 48, and closed sides 49 with a foraminous'face 46. Said spacer 45 possesses beaded edges of the same character as those possessed by the other spacer elements 35 and is mounted upon identical members 41 and 42.

To secure the several movable spacers in a closed position and in parallelism with the sta' tionary spacer, a clip 50 in the form of ya springy like U-shaped member may be employed. Said member 50 engages the internal wall of the outermost face of the top spacer clement 35 and the closed face 47 of spacer 45, said clip engag# ing any filter material which may be upon the face 47.

When the -lter is charged with a l'ter medium 'i 51, the unit may be seated in a cell 10 such as previously described. The open top of the lter ISC elements, means or strips (not shown) are provided at each side of the filter unit either on the unit or in the casing. t the bottom of the device `-or vo n baseA 19 any suitable seal may be Figure 2.

employed. Said several seals are used to make certain vthat there will be no leakage ot airbetween the casing 10 and the lter.

'Ihe lter, when loaded, is forced inwardly the casing 10 until the back edges thereof engage the stops 13 or other stops at the four corners 'of the casing 10. In securing casings 10 one to another, bolts 52 may be employed as shown in For loading and unloading the filter, a'service frame 53 is useful (see Figure 2). comprises suitable uprights and transverse members having a supporting surface adapted to receive the top strips 23 of the lter whensaid illter is inverted. 'I'he filter is held ilrmly against movement when it is disposed in said servicing frame.

To unload, the clip 50 is removedfrom the lter. Instantly, the various movable spacers 35 and spacer 45 drop downwardly, the lter being in inverted position. Filter material in strip form therebetween will drop out of its own weight or it may be dislodged manually.

Clean lter material may be inserted between. the spacers 35 andl i5-until such material 51v extends to the closed `back 30 of vthe stationary spacer 29 where such'material 30 may be secured by locks or any suitable fastening members (not shown), ,generally a long clip attached to the iframe. Thereupon each spacer member 35 and spacer in regular order is brought into horlzontal position, thus forming parallel spaced apart folds in the illter material 51. The material 5l external to the filter is cut of! from a roll or package 56 after the strip taken therefrom covers the last foraminous face of the adjacent spacer 35.. The clip 5o is then attached and-the filter is ready to lbe placed `into a housing 10 therefor.

.For loading, however,l the illter may be turned right side up, that is, stood `upon the service rack.

The movable spacer elements 35 .and 45 are kept in angular open position by suitable means until the lter material 51 lis in position thereabout and therebetween whereupon each spacer 35 and spacer 45 is permitted to drop, one at a time, into.proper horizontal position. Such assembly l forces the filter material 51 into proper position,

and each spacer element is allowed to drop into ,position without disturbing or releasing those thereabove.

Suitable manually controlled means may bel provided whereby each spacer element may be held in open position to be released one at a timel land in `proper and regular. order, or unitary means for controlling the release thereof in predetermined order may be supplied. When the' device is completely loaded, the lter material are supported at theirl open side. The open side has lips to receive wire supports or` the spacer is equipped with a hinge member of suitable type.

The arrangement' of suchl spacer members in a filter is in alternate order -with open sides being alternately oppositely disposed. f c

I claim: 1. An air filter unit comprising a supporting Said frame ments connected'to said frame and angularly movmember, spacer elements connected to said supporting member, connecting means intermediate said elements and said supporting'member admitting oit said elements being 'arranged in substantial parallelism or angularly in respect tojsaid 'supporting member, said elements being arranged in two opposed series, the elements of the opposed y series being similarly shaped and reversed, the members of said series being 'alternately disposed when said lter is in operable condition, and a continuous strip of filter material extending from the bottom of said filter to the top thereof intermediate the elements ofthe opposed series, the filter material being supported Aon opposed surfaces by opposed spacer elements.

2. An air filter comprising a supporting member, a plurality of similarly shaped spacer elements arranged invseries, each series being movably attached to said supporting member, said spacer elements 4being angularly movable with respect to one another and arrangeable-with a member of one series alternating with a member of the other series-to provide a tortuous path for a continuous s'trip of filter material, and a strip of 'filter material intermediate the members of opposedseries of spacer' elements, the opposed sides oi!` said illter being supported 4by spacer elementsofopposed series. a ,l

3. An air illter comprising aisup'portingmember, opposed series of similar spacing elements, each of .said elements having an external surface for the support of. filter material and being arranged transversely oi' the illter unit, the area of each transverse supporting surface of a spacer element being substantially equal tothe trans- 11D verse cross section of the filter unit, means for movably attaching the spacing elements to said supporting member and admitting oi'angulararrangement of said spacer elements orarrange. ment in substantial parallelism with the members 1.15

. oi.' one series alternatingwith the members ofthe other series, and a strip of lter material extending from the bottom to the top of said u nit intermediate the spacer elements4 of opposed series, said illterl material being supported on its opposite sides by members of opposed series. 4.. An air iilter comprising a frame, spacer eleable relative thereto, the spacer elements being similar in sireand shapeand being arranged in'l2.54

' in another position', and a strip of filter material extending from the bottom to the top ci. the unit and supported on opposite sides by spacer elements of opposed series.

5. In an airfilter, a retaining-member, spacing i3; elements on said retaining member, each of said spacing elements having. a surface for supporting I iilter material of an area substantially equal to the transverse cross section ofthe filter, connecting meansfrom said retaining member to said ele- |40 ments admitting of said elements being arranged in parallelism 'or in. angular position, and a strip of iilter material intermediate adjacent spacing elements.

6. In an air filter, a frame having 4opposed sides, l spacing elements intermediate said opposed'sidea' each of said spacing elements having a filter material supporting areasubstantially equal to the transverse cross section of the iilter, connecting means between said elements and said frame,

intermediate adjacent spacing elements.

7. In an air tllter, a frame, spacing elements, hinge-like connectors intermediate said frame and elements, and lter material upon said spacerelements.

8. In an air lter, a frame, spacer elements, a

connectorintermediate said frame and each of said spacer elements admitting of pivotal movement of said spacer elements,and filter material disposed upon each of said spacer elements.

9. In an air lter, a frame having sides, spacer elements on said frame, each of. said spacer elements having a filter materialsupporting area substantially equal to the transverse cross section of the lter, connecting means for alternate elements to opposite sides of said-frame to admit of the arrangement of said elements in substantial parallelism or the separation thereof where-l by to provide a continuous open space intermediate to said sides-'and lter material disposed upon each of said spacer elements.

said opposed sides, and filter material intermediate adjacent spacing elements.

A 5 11. In an air filter, a frame having opposed sides, spacing elements hingedly connected to said sides means-'for locking said elements in.

contiguity one with another, and lter material intermediate said lements.

12. In an air lter, a frame havingopposed sides, spacing elements hingedly connected to the opposed sides of said frame, alternate spacing elements being attached vto opposite sides, lter material intermediate'said spacing elements, and

a locking'member engaging one of said elements to secure all of said elements in aligned association.

13. A lter unit having a lter medium in strip form arranged in zig-zag layers and comprising a base, and spacer members hingedly connected to opposed sides of said base.

14. A lter unit having a filter medium in strip form arranged in zig-zag layers and comprising a base, and spacer elements having two spacedapart strip supporting surfaces, thevsplacer elements being hingedly connected to opposed sides of said base.

VERNER DAHLMAN.. v 

